Presenter:

Authors:

Tharith Sriv(Department of Physics, Sogang University)

Kangwon Kim(Department of Physics, Sogang University)

Hyeonsik Cheong(Department of Physics, Sogang University)

We investigated interlayer phonon modes of mechanically exfoliated few-layer 2H-SnS2 samples obtained from a SnS2 single crystal by using low-frequency micro-Raman spectroscopy. The atomic force microscope (AFM) was used to measure the sample thickness. Raman investigations were then performed using 632.8 nm, 532 nm, 514.4 nm and 441.6 nm lasers of power lower than 100 μW in a micro-Raman setup, in which the samples were measured in a vacuum chamber to avoid photo-oxidation. The intralayer Eg and A1g modes were resolved at ~206 cm-1 and ~314 cm-1, respectively. Despite the bandgap of ~2.41 eV of mono- and few-layer SnS2, which is close to the excitation energy of the 514.4 nm laser, among the lasers that we used, the 532 nm laser provided the strongest Raman signals of A1g mode as well as the interlayer shear (S1, S2) and breathing (B1, B2) modes. These interlayer modes appeared to red-shift as the thickness increased. The frequency dispersion of interlayer modes provides the characteristics for thickness determination of few-layer 2H-SnS2 by Raman spectroscopy.

*This work was funded by the Korean government through the NRF grant (NRF-2016R1A2B3008363 & No. 2017R1A5A1014862, SRC program: vdWMRC center) and by a grant (No. 2011-0031630) from the Center for Advanced Soft Electronics.